1. Field of the Invention
The present invention is related to data display apparatus, and more particularly to a display apparatus which employs a pigmented fluid to distinguish between a first and second state of individual display elements.
2. Description of the Prior Art
Presently there is a distinct separation between signage and data display technology. Signage, which typically displays a static image or images which remain displayed for relatively long periods of time, is often deployed in conditions requiring a high degree of robustness and serviceability, low power consumption, and low cost. These requirements are not met by the relatively fragile and much higher cost data displays. While the video demands of data displays require rapid refresh rates and high resolution, the refresh rates for signage are generally quite long, and their resolution is generally low. And, the overall size of signage, typically measured diagonally, is often much larger than that of data displays. Technologies currently meeting the criteria for signage are limited, and include fixed image devices such as mechanical, rotating plate or column devices and backlit scrolling signs, and basic image forming devices such as highly pixelated light-bulb based signs: However, due to the lack of alternatives, data display technology has been employed on a limited basis for certain signage applications.
There are basically three categories of data display devices: direct view, projected view, and projector devices. Direct view devices display images on a surface overlaying the pixel control mechanisms. The most common direct view devices include CRTs up to about 45 in. diagonally, and light emitting diodes (LEDs), liquid crystal displays (LCDs), and plasma field displays up to about 60 in. diagonally. Projected view devices often employ direct-view components, but enlarge the image provided by the direct-view components by reflecting the image using a series of mirrors onto a large display surface that is generally integrated with the direct view component. Most “big screen” televisions above 60 in. diagonally use projected view technology. Projector displays project an image onto an arbitrary surface. Common projected systems used CRT-based, LCD-based, and DLP (reflective micro mirror chip)-based image forming components.
Each of the aforementioned display technologies have limitations when employed as signage. For direct view devices, the pixels produced are generally quite small. Thus, a large direct view display has a large number of pixels. The cost of a direct view display above 60 inches diagonally increases approximately as the cube of diagonal screen size. And with tens of thousands of individual pixels to address, these displays are complex, difficult to service, and require significant amounts of power.
To address this, manufacturers have recently begun tiling together elements of lower-cost, smaller direct view display devices. For example, U.S. Pat. No. 6,897,855, which is incorporated herein by reference, teaches manufacturing a large-area display by abutting a number of individual LED tiles together. However, such tiled displays are still burdened by high cost, complexity of assembling and addressing, reliability, serviceability, high power consumption, etc. Furthermore, these devices are relatively fragile and not designed for exposure to inclement or other harsh conditions.
For projected view and projector displays, the quality and visibility of projected images are dependent on ambient light conditions, the surface upon which the images are projected, the brightness of the projector, and the stability of the location of the projector and surface upon which the image is displayed. For projector displays there are the added concerns about freedom from people, objects, etc. passing through the projected image path. Furthermore, there is a reciprocal relationship between the brightness of an image source, such the that providing the image in a projected view display or projector, and the lifespan of the image generating hardware. For example, the brighter the projector the shorter the life of the bulb and other projector components. For most large-area display applications, especially signage and outdoor displays, brightness, and hence contrast, is a critical measure of quality, so that from a lifespan perspective, projected view and projector displays are not optimal.
Thus, the use of data displays for signage and the like is at best a compromise, and at worst an inappropriate use of the technology. Accordingly, there is an unmet need for a low cost, reliable, serviceable, robust, large-area, variable display data device appropriate for use as signage and the like.